Late Period with Spotting?

I thought I was pregnant because my period was due on August 4th and it was late and I had all the clic pregnancy symptoms, I had taken 3 HPT's that were all 3 faint positives at the end of July and first of August. I went to my Dr. and got a blood test and it came back negative...My period or so what I thought was my period came on August 9th. It was extremely light, started out brown spotting then went to a little bit of red, then back to brown...I know it wasn't implantation, it was heavier than implanation, but lighter than a normal period. It lasted 2 days max. Now today I am spotting light pink only when I go to the restroom and wipe, it does NOT get on my panties or even require a panty liner. My periods are like clockwork, I've never had this happen before, My periods are moderately heavy and last 4-5 days. I would like some input from those this has happened to, even if it hasn't what you think it is. Do you think this could be pregnancy? I have an appt Friday with a OB/GYN, but I would just like to know your opinions too.